The present invention relates to a method for driving a plasma display panel (PDP) of a surface discharge type.
Recently, as a display device becomes large in size, thickness of the display device is desired to be thin. Therefore, various types of display devices of thin thickness are provided. As one of the display devices, an ACPDP is known.
A conventional ACPDP comprises a plurality of data electrodes (address electrodes) and a plurality of row electrodes (sustain electrodes) formed in pairs and disposed to intersect the data electrodes. A pair of row electrodes form one row (one scanning line) of am image. The data electrodes and the row electrodes are covered by dielectric layers respectively, at a discharge space. At the intersection of each of the data electrodes and each pair of row electrodes, a discharge cell (pixel) is formed. Each of the row electrodes comprises a transparent electrode and a bus electrode layered on the transparent electrode.
FIG. 4 shows a timing chart of drive signals for driving the conventional ACPDP.
A reset pulse RPx of positive voltage having a long rising time (long time constant) is applied to each of the row electrodes as sustain electrodes X1-Xn. At the same time, a reset pulse RPy of negative voltage having a long rising time is applied to each of the row electrodes Y1-Yn. Thus, all of the row electrodes in pairs in the PDP are excited to discharge, thereby producing charged particles in the discharge space at the pixel. Thereafter, when the discharge is finished, wall charge is formed and accumulated on the discharge cell (A reset all at once period).
Here, in order to regulate the discharge and emission of light caused by the reset pulse which has no connection with the display and to improve the contrast, the reset pulses RPx and RPy having long rising time (long time constant) are used.
Then, pixel data pulses DP1-DPn corresponding to the pixel data for every row are applied to the pixel data electrodes as address electrodes D1-Dm in order in accordance with display data. At that time, scanning pulses (selecting and erasing pulses) SP are applied to the row electrodes Y1-Yn in order in synchronism with the timings of the data pulse DP1-DPn.
Furthermore, priming pulses PP of positive voltage are applied to the row electrodes Y1-Yn, immediately before the scanning pulses SP are applied.
In the discharge space, the charged particles obtained by the operation of reset all at once are reduced as the time passes. Therefore, the priming pulse PP is applied to the row electrodes for reproducing the charged priming particles in the discharge space. Thus, address operation is stabilized.
At the time, only in the pixel to which the scanning pulse SP and the pixel data pulse DP are simultaneously applied, the discharge occurs, so that the wall charge produced at the reset all at once period is erased.
On the other hand, in the pixel to which only the scanning pulse SP is applied, the discharge does not occur. Thus, the wall charge produced at the reset all at once period is held. Namely, a predetermined amount of the wall charge is selectively erased in accordance with the pixel data (An address period).
Next, a discharge sustaining pulse IPx of positive voltage is applied to the row electrodes X1-Xn, and a discharge sustaining pulse IPy of positive voltage is applied to the row electrodes Y1-Yn at offset timing from the discharge row pulses IPx.
During the discharge sustaining pulses are continuously applied, the pixel which holds the wall charge sustains the discharge and emission of light (A discharge sustaining period).
In the discharge sustaining period, a first pulse of the discharge sustaining pulse IPx is set to have a pulse width wider than the subsequent pulses and the discharge sustaining pulse IPy.
The reason why the first pulse is wide will be described hereinafter.
As aforementioned, when the discharge occurs, the charged priming particles are produced, and the produced charged priming particles reduce as the time passes. As the number of charged particles reduce, the time from the application of the pulse to the start of the discharge (discharge production delay time) becomes long, and the discharge starting time at discharge cells (discharge statistics delay time) becomes uneven. In such a state, when the first pulse of the discharge sustaining pulse is applied, the discharge may not occur. Therefore, even if the subsequent pulses are applied, it is strongly possible not to occur the discharges.
Consequently, in the embodiment, the width of the first pulse is set wider than the subsequent pulses. Namely, the width of the first pulse is set larger than the sum of the discharge production delay time, the discharge statistics delay time, and the time necessary to discharge. Therefore, it is possible to ensurely produce the discharge by the first pulse of the discharge sustaining pulse IPx.
Then, wall charge erasing pulses EP are applied to the row electrodes Y1-Yn for erasing the wall charges formed on the row electrodes. Thus, the wall charges formed on the row electrodes X1-Xn and Y1-Yn are erased, whereby the wall charges in the lighted and unlighted pixels are approximately uniformed (A wall charge erasing period).
In the driving method of the PDP, the reset pulse having a gentle waveform at the rise is applied to the row electrodes all at once, thereby resetting all at once. In the discharge sustaining period, the pulse width of the first pulse of the discharge sustaining pulse which is applied to the row electrodes X1-Xn is set to a large width.
In the conventional method, the reset pulse having the long time constant is employed for weakening the reset discharge, thereby improving the contrast. However, since the reset discharge is weak because of the reset pulse of the long time constant, the amount of priming particle (charged particle) formed in the discharge space is small. Therefore, the priming pulses PP are applied immediately before the scanning pulses SP for reproducing the priming particles which are produced when the reset discharge occurs and reduce as the time passes in the discharge space so as to stabilize the address operation.
On the other hand, in order to display the PDP of high definition, it is necessary to write the display data at a high speed in the address period. However, in the address period, on about the lines including at least a line to be scanned first, the timing of priming discharge by the priming pulses PP becomes uneven. Therefore, selecting and erasing discharge produced by the selecting and erasing pulse (scanning pulse) applied immediately after the priming pulse becomes unstable.
The reason will be described. On a subsequent line which is scanned after the scanning of lines including the first scanning line, since the priming discharge (and selecting and erasing discharge) has occurred on the line at the upper side of the subsequent line, a large amount of priming particles are applied to the subsequent line to be scanned at the time. Thus, the discharge easily occurs on the subsequent line. To the contrary, on the lines including the first scanning line, since the amount of priming particles is small, the lines are in a difficult condition to occur the discharge.